Pipelines are commonly used to transport material such as gas, oil, slurry or similar substances over long distances. Such pipelines are normally made out of metal and are commonly joined together with welds. In refineries, pipelines are used to transport material from one portion of the refinery to another. The pipeline may (or may not) be covered with insulation.
Such pipelines may corrode and, if the corrosion is not detected early enough, the pipelines may start to leak. If the leak is not detected early, catastrophic results may occur, including fires and/or explosions. Preferably, the corrosion is detected before a leak ever occurs.
Non-destructive testing, including the use of x-rays or gamma rays penetrating the pipeline, is used to determine if a pipeline has defects therein as may typically be caused by corrosion. U.S. Patent Publication No. US 2012/0201347 A1, published on Aug. 9, 2012 by Prentice et al. and assigned to Shawcore Ltd. shows a method and apparatus for inspecting pipelines to determine if there are any defects in a pipeline. However, the Prentice patent is difficult to install and requires access to the entire circumference of the pipeline. If a pipeline is in a refinery and is supported on support beams, the Prentice invention cannot inspect the pipe where the pipe touches the support beam.
In pipelines, if the pipeline is buried, non-destructive testing of the buried pipeline is normally made by sending a pig through the pipeline. The pig is typically made up of (a) a drive package, (b) a flux loop that does the sensing and (c) a recorder package. Using such a pig, the entire Trans Alaska Crude Oil Pipeline was tested in 1997. However, for many pipelines, especially in refineries or processing plants, a pig cannot be run through the pipeline. Also, many of the pipelines are covered with insulated material which prevents direct access to the pipeline.
The purpose of the non-destructive testing is to use a non-invasive technique to determine the integrity of a pipe or quantitatively measure any corrosions or defects in the pipe. Non-destructive testing inspects and measures without doing harm to the pipe. There are many different ways of non-destructive testing, including, but not limited to, (a) acoustical emissions, (b) ultrasonic, (c) eddy current, (d) magnetic measurements, (e) microwave, (f) flux leakage or (g) x-ray. The use of x-rays or gamma rays is one of the more common techniques for non-destructive testing. In the use of x-ray or gamma ray technology for non-destructive testing, the pipe being tested is placed between the radiation source and a detector. The less radiation that reaches the detector, the better the pipe. The more radiation that reaches the detector, the more wear or corrosion in the pipe.
In industrialized countries such as the United States, many refineries or processing facilities were built years ago. Over time, corrosion or erosion can cause the pipes in the plant to wear thin and eventually leak. If a pipe leaks, depending upon what is being moved through the pipe, the leak can cause catastrophic results. The detection of a thin section of pipe before it leaks can be very critical.
The use of non-destructive testing for pipelines has become so common that standards have been developed by ASTM International. A collection of ASTM standards under “Radiology (X and Gamma) Method” have been developed.
One of the entities that has performed non-destructive testing on insulated pipes in the past is IHI Southwest Technologies, Inc. located in San Antonio, Tex., assignee of this invention. IHI has developed digital radiograph tools for detecting internal and external corrosion in insulated piping. Generally, a radiation source will create a radiation beam that penetrates a pipe under test. The radiation beam will penetrate not only the pipe, but also insulation there-around. A detector array is located on generally the opposing side of the pipe being inspected using a radiation source. In this manner, the detector array can determine if there is any corrosion and the severity of the corrosion. However, the prior systems developed by IHI were very complex and hard to move along a pipe being inspected to give good results. Also, dead zones would occur that were not being penetrated by the radiation. Because of the difficulty in installation and maneuverability of the prior digital radiographic imaging by IHI, it was difficult to eliminate the dead zones. The prior developed digital radiographic tool requires a lot of time to install and operate.